The cheapest I've seen the D3 is $599 shipped (http://www.everyprice.com/item.asp?item ... YAodkSyOpw). But then you need to buy your accessories (iPod adapter, steering wheel control, harness/cage, etc. I'd get the accessories on eBay.
I think for ~$700 for total, it's a helluva deal. I agree, get an iPod/Sattelite Radio so you can toggle between NAV and your music with no interruption. Think about it.......copying your music (MP3s) to CD/DVD is old skewl. Why not just keep it on one place, your iPod, and take it wherever you go? This is why the single DVD slot works fine.